A conventional quick release device for connecting the axle 2 of a front wheel to the two legs 21 of front fork or for connecting the axle of a rear wheel to the chain stays is shown in FIG. 1 and generally includes an operation member 1 which is composed of a lever 15 and a cam portion 16 which includes a curved periphery 17. A rod 11 has one end connected to the cam portion 16 and the other end of the rod 11 extends through a cooperation unit 12, one of the legs 21 of the front fork, the axle 2 of the front wheel, the other leg of the front fork and is threadedly connected with a nut 13 by a threaded section 14 of the rod 11. Each leg 21 of the front fork includes a recessed area 23 defined in an outside thereof so as to receive the cooperation unit 12 and the nut 13 when the quick release device secures the parts mentioned above. The two legs 21 of the front fork each have an open end 22 in which the rod 11 is engaged, and the user operates the operation member 1 to lock the quick release device. However, the rod 11 is easily disengaged from the two open ends 22 of the two legs 21 before pivoting the operation member 1 because there is no proper positioning device to locate the legs 21 and the rod 11.
An improved quick release device is disclosed as shown in FIG. 2, wherein a biasing unit 3 is added to the conventional quick release device as shown in FIG. 1 and located between the leg 21 and the cooperation unit 12. The biasing unit 3 includes a cup 31 and a spring 32 which has one end contacting an inside of the cup 31 and the other end is in contact with the cooperation unit 12. The spring 32 applies a force to pull the rod 11 before the operation member 1 is pivoted such that the leg 21 can be clamped between the axle 2 and the biasing unit 3. This improves the shortcoming of the conventional quick release device as shown in FIG. 1. Nevertheless, the biasing unit 3 is exposed and easily contaminated by mud and dust. The spring 32 might jump out from the opened end of the cup 31 when assembling the quick release device.
The present invention intends to provide a quick release device with a biasing unit which is a tubular combination so as to protect the spring therein from mud and dust.